1. Field of the Invention
The present invention relates to a method for protecting a security data memory and a security processor having such a security data memory. The terms “security data memory” and “secured data storage” as used herein refer to any data memory or protected data storage containing security-relevant data which must be protected from unauthorized access.
2. Description of Related Art
Such security processors having security data memories are found in particular in smart cards and smart card terminals used to make a data link with a smart card. Since the security-relevant data are stored on the smart cards in coded form, the security processor must be in possession of the right keys to be able to process the smart card data. Said keys are stored in a security data memory. In order to prevent unauthorized persons from acquiring said key data and committing abuse with them, special measures are necessary.
The applicant's EFTPOS terminal is already known from practice. With this terminal the total security module with the security processor including display, keyboard and measuring heads is cast as one unit. A light sensor is located within the casting compound. As soon as said light sensor detects incidence of light, the security processor automatically erases the security-relevant data stored in the security data memory. Unauthorized access from outside would make the terminal inoperable, but a readout of the security-relevant data would no longer be possible.
EP 0 408 456 B2 describes a smart card whose microcircuit is protected from access by a plurality of sensors having a so-called state of prestress. Said sensors react to mechanical deformations. A plurality of sensors are distributed within the smart card in order to monitor the total smart card for attacks.
Said known security measures are reliable, but it is hitherto not possible to obtain information on how an attack was performed after a sensor responds, i.e. after an attack has occurred.